BRAF and metastatic colorectal cancer: Mutations in KRAS at codon 12 or 13 (observed in 35% to 45% of cases) or the v-raf murine sarcoma viral oncogene homolog B (BRAF) V600E mutation (approximately 10%) confer resistance to cetuximab-based therapies in metastatic colorectal cancer (mCRC) [38].